Post-weld friction stir processing of AA5083-F TIG welds with scandium added fillers

Abstract

Abstract TIG welded marine grade AA5083-F/ER5356 and AA5083-F/ER5356+Sc joints were friction stir processed with a pin less FSP tool, to explore the impact of the process parameters on the mechanical and metallurgical characteristics of the weldments and enhance the weld strength. The microstructure of the welds was observed using optical and SEM and subjected to mechanical tests like impact toughness, tensile, microhardness and fractography, to evaluate the strength of the weld. A microstructural improvement was observed in the FSPed weld joints, with an average grain size of 4 μm for TIG welds and 2 μm for Sc added TIG welds, in comparison to the TIG-welded joints, which showed an average grain size of 12 μm and 8 μm when Sc was added. The ultimate tensile strength (UTS) of the FSPed joints were higher than the tensile strength of the base metal, with values of 288 MPa for the FSPed joints and 331 MPa for the Sc added FSPed joints. The FSPed joint’s elongation range decreased to 7.1% but showed a marked improvement for the Sc added FSPed joints, up to 20.5%. There was a marked improvement in the maximum hardness compared to TIG welded joints, with the FSPed TIG-welded joints giving a value of 90 HV1, while the maximum hardness of Sc added FSP joints showing 95 HV1. The study revealed that FSPed and Sc added joints improved the mechanical and microstructural properties of the TIG welded joints significantly.